This invention relates to a centrifugal governor for use with an internal combustion engine, and more particularly to means for releasing the adaptation mechanism of the centrifugal governor at partial load operation of the engine.
A conventional centrifugal governor for internal combustion engines is generally provided with an adaptation mechanism (plus adaptation mechanism) which is adapted to cause displacement of the control rack in a fuel quantity decreasing direction in medium and high engine speed ranges to increase the output torque of the engine in the same ranges.
A centrifugal governor is already known which is equipped with an adaptation mechanism which comprises an adaptation spring arranged to counteract displacement of flyweights in a fuel quantity decreasing direction; a supporting lever engaging at its intermediate portion with a control lever which is manually operatable, at its one end with a tension lever biased in a fuel quantity increasing direction by a control spring, and at its other end with a floating lever engaging with the control rack, respectively; a fuel quantity increasing lever engaging at its one end with a guide lever connected between a shifter movable with the flyweights and the tension lever, and at its other end with the floating lever, respectively; and an adjusting member carried by the tension lever with its one end disposed for urging contact with an intermediate portion of the fuel quantity increasing lever. When the engine rotational speed exceeds a predetermined value, the adjusting member comes into urging contact with the fuel quantity increasing lever as the shifter is moved in the fuel quantity decreasing direction. Further movement of the shifter causes contraction of the adaptation spring, which in turn causes angular displacement of the fuel quantity increasing lever in the fuel quantity increasing direction.
In the above-mentioned type adaptation mechanism, the adjusting member is held stationary at a preset position on the tension lever, and is disposed for urging contact with the fuel quantity increasing lever in dependence on the angular position of the supporting lever and the position of the shifter. Thus, the adaptation mechanism acts to increase the fuel injection quantity not only at engine full load but also at engine partial load in medium and high engine speed ranges, which involves the following problems:
(1) In the medium and high engine speed ranges where the fuel injection quantity increases due to the action of the adaptation mechanism, the actual output torque of the engine exceeds a required value corresponding to actual load on the engine. Therefore, even slight stepping-on of the accelerator pedal causes an large increase in the engine rpm, whereas it is difficult to carry out stable control of the engine rpm during constant-speed running of the vehicle. PA1 (2) Upon transition from a low engine speed range to a medium or high engine speed range (fuel quantity-increased range), there can occur a sudden increase in the fuel injection quantity, which brings about unbalance between the increased engine speed and the actual vehicle speed, causing knocking of the vehicle.